Author Topic: Dual MOT tesla coil  (Read 1502 times)

Offline Jun

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Dual MOT tesla coil
« on: August 02, 2020, 01:07:54 PM »
Hi Guys!
Thanks to this forum's support, I was able to complete my Dual MOT tesla coil which can create arc over 1.5m long
I have built several tesla coils in the past like Mosfet slayer exciter or Flyback tesla coil, but this was my first Legit tesla coil.
my SGTC draws 25A from the mains (6000W) as my inductive MOT ballast which I salvaged from Japan does not limit current enough, but breaker takes some time to trip.
/>Specs:
Primary capactior-18kV 49nF
 (capacitor used Wima FKP 4 1kV 220nF 18S4P (very cost effective capacitor and can stand 750kHz from my smaller SGTC)
Primary coil-1/2 inch copper tubing up to 10 turns
secondary-coil 6'' wound on PVC
Topload-Aluminium ducting covered with aluminium tape
Spark gap - Static spark gap made from copper tubing
Again. Thanks guys!

Offline MRMILSTAR

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Re: Dual MOT tesla coil
« Reply #1 on: August 02, 2020, 04:55:14 PM »
Nice looking coil. It sounds like someone didn't like what they saw.  :)
Steve White
Cedar Rapids, Iowa
Retired electrical engineer

Offline Jun

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Re: Dual MOT tesla coil
« Reply #2 on: August 02, 2020, 05:10:12 PM »
Hehe. Nah actually, my little step brother has been asking me to build lightning machine. So I did. The scream was from him sitting right next to me with joy

Offline Jun

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Re: Dual MOT tesla coil
« Reply #3 on: August 03, 2020, 05:23:15 PM »
I was thinking of adding two extra MOTs for more power. I have already built mmc bank for added MOTs but my construction is already at its limit as spark does occasionally strike the ground rail. What can I do?

Offline MRMILSTAR

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Re: Dual MOT tesla coil
« Reply #4 on: August 03, 2020, 08:30:38 PM »
I have seen 4 MOTs used in series-parallel. I doubt if you can reliably put 4 in series because the voltage would exceed the capacity of the insulation of the windings. Phasing is critical.

A more radical solution for those that want more power is to use a pole transformer. That's what I use. Then your worries about available power go away.
« Last Edit: August 03, 2020, 08:32:47 PM by MRMILSTAR »
Steve White
Cedar Rapids, Iowa
Retired electrical engineer

Offline Teravolt

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Re: Dual MOT tesla coil
« Reply #5 on: August 03, 2020, 09:17:40 PM »
are the mots in your setup in series or parallel.

Offline Jun

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Re: Dual MOT tesla coil
« Reply #6 on: August 04, 2020, 08:43:00 AM »
my current setup is dual MOT 180 degrees phaseshifted to get around 4kV. I have already made 4 MOT in series with no oil insulation and it worked fine.

Offline Jun

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Re: Dual MOT tesla coil
« Reply #7 on: August 04, 2020, 08:47:07 AM »
I might try 4 MOT series parallel configuration. I would have to modify my mmc bank but it sounds nicer.

Offline davekni

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Re: Dual MOT tesla coil
« Reply #8 on: August 05, 2020, 11:48:55 PM »
My dual-MOT SRSGTC has the two MOTs stacked with one end ground.  Wanted one side of the spark gap grounded for easier rotary-gap construction.  It did require removing the secondary-to-core connection on the second MOT, and epoxy insulation around inside edges of the secondary winding to prevent arcing to the core.  Thus it would be possible to stack 4 MOTs with the center grounded.  That impedance would fit your 49nF MMC better.

BTW, my SRSGTC uses separate line cords for each MOT to get more power than a single 120V 15A circuit allows.  I have a DPDT switch to select phasing depending on whether the two line circuits are in-phase or 180 degrees out-of-phase.  (This is for US residential power which is single-phase 240VCT.)  I also added extra series inductors on the MOT primaries to tune for resonant charging.
David Knierim

Offline Jun

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Re: Dual MOT tesla coil
« Reply #9 on: August 06, 2020, 03:53:58 PM »
Cool. I have already successfully removed secondary wire from the iron core of MOT. (Destroyed few MOTs in process). I would submerge MOTs in oil for insulation and hopefully I can create nice 8kv power supply.

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Re: Dual MOT tesla coil
« Reply #9 on: August 06, 2020, 03:53:58 PM »

 


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